ROT13 Cipher

What Is ROT13?

ROT13 ("rotate by 13 places") is the simplest Caesar cipher variant — each letter shifts 13 positions through the alphabet. Because the English alphabet has exactly 26 letters, applying ROT13 twice always returns the original text, meaning encode and decode are the exact same operation. It was popularized in online forums and Usenet groups to hide spoilers, puzzle answers, and off-topic content from casual readers. ROT13 provides no real cryptographic security; it is purely a light obfuscation technique. Non-alphabetic characters — digits, punctuation, spaces — pass through unchanged. Everything runs entirely in your browser with no data sent to any server.